Method and apparatus for detecting failure in solar cell module, and solar cell module

ABSTRACT

In the present invention, the temperature of a bypass diode of a solar cell module is measured by a temperature detection means from the exterior of the solar cell module, and the results of temperature detection on each bypass diode are mutually compared to detect the presence or absence of the failure in the solar cell module. Also at least one solar cell in the solar cell module is covered with a light shielding plate, then a current flowing in the bypass diode bypassing to the covered solar cell is detected, and a failed solar cell module is detected from the result of the current detection. Also the solar cell module is provided with a temperature detection means capable of detecting the temperature of the bypass diode and the temperature of an internal portion of the solar cell module other than the bypass diode. By these, it is rendered possible to detect a failure in the solar cell module easily and exactly, and also to detect the short circuit failure in the solar cell.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method and an apparatus fordetecting a failure in a solar cell module in a photovoltaic powergeneration system, and to a solar cell module.

[0003] 2. Related Background Art

[0004] Because of the recently increased concern for the environmentaland energy issues developing in the global scale, the photovoltaic powergeneration system is attracting attention as a clean energy source. Forinstallation, the solar cell is constructed as a ground installationtype for installation on the field or a roof installation type forinstallation on the house roof, but the latter capable of effectivelyutilizing the roofs of the houses is mainly used because theinstallation of solar cells requires a large area. The roof installationtype can be principally divided into a type for installation on asupport and a type integrated with the roof material, but recently thereis increasing the roof material-integrated solar cell module in whichsolar cells are stacked on a roofing steel plate and which has thefunction of the roof material.

[0005] In constructing a photovoltaic power generation system, a solarcell array is constructed by understanding the characteristics of thesolar cell module and determining the number of series and parallelconnections of the solar cells in order to obtain a desired outputthereof. FIG. 2 is a block diagram of a general photovoltaic powergeneration system.

[0006] A solar cell array 20 is produced by connecting a plurality ofsolar cell modules in series to form a string and then by connecting aplurality of strings in parallel. In the photovoltaic power generationsystem, a direct current from the solar cell array 20 is collected at ajunction box 50, then supplied to an inverter 60, and further suppliedto a load 40 through a power distribution board 70. In the photovoltaicpower generation system for ordinary house, the junction box 50 and theinverter 60 are often installed indoors for facilitating maintenance andinspection. Each solar cell module is provided with a bypass diode, and,in the case of an unbalance in the currents of the solar cell modules,the current bypasses the solar cell module to flow in the diode. Inorder to achieve the safe and efficient operation of the photovoltaicpower generation system, it is essential to exactly detect the failurein the solar cell module.

[0007] For detecting a failure in a solar cell module, there areconventionally known, for example, a method of measuring the terminalvoltage of solar cell modules with a tester and finding out the solarcell module of a lowered terminal voltage, a method of employing a lightemitting diode as a bypass diode provided in a solar cell module andinspecting the light emitting state of the diode as disclosed inJapanese Patent Laid-Open No. 8-97456, and a method of providing meansfor changing color by a current flowing in a bypass diode of the solarcell module, in a solar cell module, as disclosed in Japanese PatentLaid-Open No. 9-148613.

[0008] However, in the above-mentioned method of measuring the terminalvoltage of the solar cell, it is necessary to measure the terminalvoltage of each solar cell module with a voltage detecting device suchas a tester, and such measurement is very difficult particularly in thecase the solar cell module is installed on the roof, because the wiringsof the solar cell module are usually formed on the back face thereof.

[0009] Also in the method of detecting a failed solar cell module byemploying a light emitting diode as the bypass diode provided in thesolar cell module as disclosed in Japanese Patent Laid-Open No. 8-97456,a current flows in the light emitting diode even in a partial shadestate in which the solar cell module is partially shaded, whereby thelight emitting diode is turned on. Also the forward voltage drop of thelight emitting diode is much larger than that in the ordinary diode.Therefore, the light emitting diode generates a large loss and wastes aprecious power generated in the solar cell.

[0010] Furthermore, in Japanese Patent Laid-Open No. 9-148613, a currentflowing in the bypass diode of the solar cell module is detected by acolor changing member incorporated in the solar cell module and capableof changing color by a temperature change, and a failure in the solarcell module is found out by inspecting a color change in a single colorchanging member. However, the temperature of the solar cell module mayrise to about 80° C. under the strong solar radiation energy in the midsummer time, and it is impossible to find out a failure in the solarcell module by merely observing a color change in a single colorchanging member, in consideration of a case where a temperature rises to80° C. in the bypass diode connected to a normal solar cell module insummer and a case where a temperature rises to 80° C. in the bypassdiode by a failure in the solar cell module.

[0011] Also among the failures of the solar cell, there is known shortcircuit failure caused by the short circuit of the solar cell. In thesolar cell with the short circuit failure, no current flows in thebypass diode, so that the short circuit failure cannot be detectedsolely by the conventional method of detecting a current flowing in thebypass diode.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide a method and anapparatus for detecting a failure in a solar cell module, and a solarcell module which allow to easily detect the failure in the solar cellmodule even when it is installed on a roof. Another object of thepresent invention is to enable exact detection of the failure in thesolar cell module even in the case of employing the color changingmember incorporated in the solar cell module and capable of changingcolor by a temperature change. Still another object of the presentinvention is to enable easy detection of the short circuit failure ofthe solar cell module.

[0013] In order to attain the above-mentioned objects, the method of thepresent invention of detecting a failure in a solar cell modulecomprises detecting the temperature of a bypass diode of the solar cellmodule from the exterior of the solar cell module and detecting thepresence or absence of the failure therein based on the result of thetemperature detection. Also the apparatus of the present invention fordetecting a failure in a solar cell module comprises a temperaturedetecting means for detecting the temperature of a bypass diode of thesolar cell module from the exterior of the solar cell module.

[0014] Thus, when the solar cell module is installed, for example, onthe roof, the failure in the solar cell module can be easily detectedfrom the top side thereof even if the solar cell module does not havethe temperature detecting means therein.

[0015] Also, another method of the present invention of detecting afailure in the solar cell module comprises covering at least one solarcell in the solar cell module with a light shielding plate, detecting acurrent in a bypass diode bypassing the covered solar cell, anddetecting the failed solar cell module based on the result of thecurrent detection. Further, another apparatus of the present inventionfor detecting a failure in a solar cell module comprises a lightshielding plate for covering the solar cell module or a solar cell, acurrent detection means for detecting a current in a bypass diodebypassing the solar cell module or the solar cell, and means fordetecting a failed solar cell module based on the output from thecurrent detection means.

[0016] It is thus possible to easily and exactly detect the solar cellmodule with a short circuit failure by utilizing a current flowed in thebypass diode when a normal solar cell module or a normal solar cell isshielded from light.

[0017] Further, the solar cell module of the present invention comprisesa temperature detection means provided in the exterior of the solar cellmodule and capable of detecting the temperature of a bypass diodetherein and the temperature of an interior of the solar cell moduleother than the diode.

[0018] When there is employed a color charging member incorporated inthe solar cell module and capable of changing color by the temperaturechange, the temperature of a bypass diode can be evaluated in relativecomparison with the temperature in the surrounding solar cell moduleunder a similar environment, whereby the failure in the solar cellmodule can be accurately detected.

[0019] Furthermore, the solar cell module of the present inventioncomprises, in the vicinity of the bypass diode, means for preventing thetemperature rise of a bypass diode resulting from a cause other than acurrent.

[0020] By employing this module and measuring the temperature rise inthe bypass diode with the above-described method, it is possible toavoid the difficulty in the failure detection resulting from a fact thatthe bypass diode becomes excessively heated, for example, by the directsunshine and the specific heat generated by the bypass diode itself cannot be discriminated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a constitutional diagram illustrating a method ofdetecting a failed solar cell module according to Example 1 of thepresent invention;

[0022]FIG. 2 is a block diagram showing a general photovoltaic powergeneration system;

[0023]FIG. 3 is a diagram illustrating the principle of one method ofthe present invention of detecting a failed solar cell module;

[0024]FIG. 4 is a diagram illustrating the principle of another methodof the present invention of a failed solar cell module;

[0025]FIG. 5 is a diagram illustrating another principle of anothermethod of the present invention of detecting a failed solar cell module;

[0026]FIG. 6 is a diagram illustrating still another principle ofanother method of the present invention of detecting a failed solar cellmodule;

[0027]FIG. 7 is a diagram illustrating a solar cell module (amorphoussilicon solar cell SR-03 manufactured by CANON) employed in theconfiguration shown in FIG. 1;

[0028]FIG. 8 is a diagram illustrating a method of detecting a failedsolar cell module according to Example 3 of the present invention;

[0029]FIG. 9 is a diagram illustrating a solar cell module with atemperature detection means in the interior of the module according toExample 4 of the present invention; and

[0030]FIG. 10 is a diagram illustrating a solar cell module (amorphoussilicon solar cell BS-04 manufactured by CANON) according to Example 5of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] In a preferred embodiment of the method and apparatus of thepresent invention for detecting a failure in a solar cell module, thepresence or absence of the failure in the solar cell module is detectedby mutual comparison of the results of temperature detection in eachbypass diode.

[0032] Specifically, in the case of breaking of a wire in a solar cell 1among solar cells constituting a solar cell module 10, a current doesnot flow in the failed solar cell 1 but in a bypass diode 15 bypassingthe solar cell 1. This failure is called an open circuit failure. Insuch state, the bypass diode 15 in which a current flows shows atemperature rise in comparison with other bypass diodes 15 in which acurrent does not flow.

[0033] It is therefore possible to search the module 10 including thebypass diode in which a current flows, that is, the solar cell 1 in theopen circuit failure state, by detecting the temperature of the bypassdiodes 15 in the solar cell module 10 from the exterior of the module byuse of a failure detecting apparatus provided with a temperaturedetecting means 30 as shown in FIG. 1 and by executing relativecomparison of the temperature difference between the bypass diode 15 ofthe normal solar cell 1 and the bypass diode 15 of the failed solar cell1. This search may however become difficult when the temperature of thebypass diode 15 becomes excessively high, for example, by directsunlight. Therefore, in the solar cell module of the present invention,the bypass diode 15 may be provided in the vicinity thereof with meansfor preventing a temperature rise generated from any cause other than acurrent. Specifically, the bypass diode 15 may be covered with a lightshielding member such as a reflecting plate, or surrounded by a heatinsulating material. The failure detecting apparatus as shown in FIG. 1can be applied to the failure detection of this module.

[0034] Also in an embodiment of another method and apparatus of thepresent invention for detecting a failure in a solar cell module, acurrent flowing in the bypass diode bypassing a solar cell covered witha light shielding plate is detected either by detecting a magnetic forcegenerated by the current, or by a light emitting member which emitslight by the current, or by detecting the temperature of the bypassdiode and/or solar cell of the solar cell module.

[0035] More specifically, in the case where a solar cell 1 generateselectric conduction (called a short circuit failure) as shown in FIG. 4,a current flows in the failed solar cell similarly to the normal one, sothat the failure cannot be easily detected. In such case, the solarcells 1 are covered one by one with a light shielding plate. A normalsolar cell 1 covered with the light shielding plate functions as a diodeconnected in the inverse direction, so that a current cannot flow insuch solar cell. Consequently, as shown in FIG. 5, a current flows inthe bypass diode 15 connected to such normal solar cell covered with thelight shielding plate 80. On the other hand, a current can flow in thesolar cell 1 with a short circuit failure as shown in FIG. 6, even whenit is covered with the light shielding plate 80. It is thereforepossible to search the failed solar cell 1 with the short circuitfailure, by covering the solar cells 1 one by one with a light shieldingplate 80 and detecting a solar cell 1 having the bypass diode 15 inwhich a current does not flow.

[0036] The temperature detection of the solar cell 1 in the embodimentsshown in FIGS. 3 and 5 to 6 may be executed by a temperature detectingmeans of non-contact type or contact type. Also as the temperaturedetection means, there may be used a visual temperature detection meansemploying a color changing member capable of reversibly changing colorby a temperature change. However, there is preferred a thermometer whichshows a concrete temperature value since the failure can be more exactlydetected.

[0037] In another preferred embodiment, the solar cell module of thepresent invention is provided with a temperature detection means capableof simultaneously detecting the temperature of the bypass diode and thetemperature of the interior of the solar cell other than the bypassdiode. As the temperature detection means, there can be used a visualtemperature detection means, for example, a color changing membershowing a reversible color change by a change in the temperature. Thus,by merely looking at the color of the color changing member provided inadvance in the interior of the solar cell module, the presence orabsence of a current flowing in the bypass diode can be readilyunderstood, so that the presence of a failure in the solar cell modulecan be extremely easily judged.

EXAMPLE 1

[0038]FIG. 1 is a constitutional diagram illustrating the method ofdetecting a failure in the solar cell module according to Example 1 ofthe present invention. FIG. 7 shows a solar cell module (amorphoussilicon solar cell SR-03 manufactured by CANON) integrated with aconstruction material. As shown in these drawings, a solar cell module10 is composed of six solar cells 1 connected in series, and a bypassdiode 15 is connected to each of the solar cells 1.

[0039] As shown in FIG. 1, a load 40 was connected to the solar cellmodule 10 in which one of six solar cells 1 had an open circuit failure,and the temperature of the bypass diode 15 connected to each of thesolar cells 1 was measured with a temperature detection means 30,specifically a radiation thermometer. At this measurement, the solarradiation energy was 0.9 kW/m², and the generated current was 2.5 A. Themeasured temperatures of the bypass diodes 15 are shown in Table 1.TABLE 1 Solar cell No. 1 2 3 4 5 6 Bypass diode temp. (° C.) 53 52 53 5353 53

[0040] In comparison with the temperatures of the bypass diodes 15, itis found that the temperature of the bypass diode 15 connected to thesecond solar cell 1 is higher by about 40° C. than the temperature ofother bypass diodes 15. It can therefore be found out that a currentflows in such bypass diode 15, namely that the second solar cell 1 hasan open circuit failure.

[0041] In this example, the failure in the solar cell 1 could berelatively easily detected because the bypass diode 15 in which acurrent flowed showed a larger temperature rise by about 40° C. thanthat of other bypass diodes 15 in which a current did not flow, but themagnitude of such temperature rise may vary depending on the situation.However, such magnitude of the temperature rise can be easilycalculated, for example, from the magnitude of a current flowing in thebypass diode 15, the heat resistance and heat radiation area of thebypass diode 15. It is also effective to provide the aforementionedmeans for preventing the temperature rise.

[0042] As explained in the foregoing, it is possible to find out thefailed solar cell 1 by measuring the temperature of each bypass diode 15and comparing the measured temperatures of the bypass diodes with oneanother.

EXAMPLE 2

[0043] In the following there will be explained Example 2 in which thepresent invention is executed under a high temperature environment.

[0044] In this example, there was employed the solar cell module used inExample 1, in which one solar cell had an open circuit failure. Thesolar cell module was placed in an environmental test chamber set at 70°C., and was irradiated with an artificial solar light from a metalhalide lamp, instead of the sunlight.

[0045] The solar cell module was connected to a load, and thetemperature of the bypass diode connected to each solar cell wasmeasured with a radiation thermometer.

[0046] At the measurement, the temperature of the solar cell module was91° C., the solar irradiation energy was 0.7 kW/m², and the generatedcurrent was 2.0 A. The measured -temperatures of the bypass diodes 15are shown in Table 2. TABLE 2 Solar cell No. 1 2 3 4 5 6 Bypass diodetemp. (° C.) 93 124 93 92 94 93

[0047] In comparison-with the temperatures of the bypass diodes, it isfound that the temperature of the bypass diode 15 connected to thesecond solar cell 1 is higher by about 30° C. than the temperature ofother bypass diodes.

[0048] It can therefore be found that a current flows in the bypassdiode connected to the second solar cell, namely that the second solarcell has an open circuit failure.

[0049] As explained in the foregoing, the bypass diode in which acurrent flows is higher in temperature rise than other bypass diodes inwhich a current does not flow even at a high temperature, so that it isrendered possible, regardless of the external temperature, to search thefailed solar cell by measuring the temperature of each bypass diode andcomparing the measured temperatures of the bypass diodes with oneanother.

EXAMPLE 3

[0050]FIG. 8 is a diagram illustrating the method of detecting a failurein a solar cell module according to Example 3 of the present invention.This example employed an amorphous silicon solar cell SR-03 manufacturedby CANON in which one solar cell had an open circuit failure similarlyto Example 1. As shown in FIG. 8, a load 40 was connected to the solarcell module 10. As the temperature detecting means on the bypass diode15 connected to each solar cell 1, a thermotape (manufactured by NichiyuGiken Kogyo Co., Ltd.) 35 of a size of 1 cm×1 cm was adhered onto thesurface of the solar cell module 10 as temperature detection means. Thethermotape 35 shows a color change by a change in the temperature, andthis example employed a thermotape TR-70 which showed a reversible colorchange from red to brownish purple at 70° C. At the measurement, thesolar radiation energy was 0.8 kW/m², and the generated current was 2.3A. In the observation of the color of the thermotapes 35 attached to thebypass diodes 15, five thermotapes 35 remained unchanged in red color,but the thermotape 35 on the bypass diode 15 connected to the secondsolar cell showed a color change from red to brownish purple. It couldtherefore be found that a current flowed in such bypass diode 15, namelythat the second solar cell 1 had an open circuit failure.

[0051] As explained in the foregoing, it is possible to visually detectthe failure in the solar cell module by measuring the temperature ofeach bypass diode 15 with the temperature detecting means showing acolor change by a change in the temperature, such as the thermotape 35.

[0052] In the photovoltaic power generation system for the ordinaryhouse, the junction box, the inverter and the like are often installedin the attic so that it is difficult to electrically detect the failurein the solar cell module. The constitution of the present example allowshowever to easily detect the failure in the solar cell module.

[0053] The present example employed the thermotape as the temperaturedetection means which shows a color change in response to the change intemperature, but there may also be employed a thermolabel, athermosheet, a thermopaint or a thermocrayon (all manufactured byNichiyu Giken Kogyo Co., Ltd.) which is prepared by forming a paintshowing a color change in response to a temperature change into a label,a sheet, paint or a crayon. However, the color changing member ispreferably capable of reversibly changing color, since a current flowsin the bypass diode 15 connected to the solar cell 1 which is in apartial shade state (namely in a state of the solar cell shaded from thesunlight).

[0054] In the present example, the theromtape capable of changing colorat 70° C. was used, but it is possible to execute the temperaturemeasurement under various conditions, for example, by using a piece of atheromtape capable of changing color at 50° C., 60° C., 70° C., 80° C.,90° C. and 100° C. by multistage.

[0055] In the present example, the temperature of the bypass diode 15can be measured from the surface of the solar cell module 10, because itemploys an extremely thin resin as the surface protecting material.

EXAMPLE 4

[0056]FIG. 9 is a diagram illustrating the constitution of a solar cellmodule according to Example 4 of the present invention. As shown in FIG.9, this example employs a solar cell module 10 provided with atemperature detection means in the interior thereof. The solar cellmodule 10 is featured by employing, as the temperature detection means,a thermotape 35 which is arranged so as to measure the temperature ofthe bypass diode 15 in the solar cell module 10 and the temperature of aportion of the module 10 other than bypass diode 15.

[0057] Generally, the surface temperature of the solar cell module 10 issubstantially the same under the same solar irradiation energy. However,when a current flows in the bypass diode 15 by an open circuit failurein the solar cell module 10, the temperature of such bypass diodebecomes higher than that in other portion of the solar cell module 10.Consequently, in the thermotape 35 provided in an area containing suchbypass diode 15, a portion thereof positioned on the bypass diode 15changes color in comparison with other portion.

[0058] Instead of relative comparison of the temperature of other bypassdiodes, it is therefore possible to judge whether a current flows in thebypass diode 15 and to search the failed solar cell 1, in relativecomparison of the temperature of the bypass diode 15 with thetemperature of a vicinity thereof subjected to the same solar radiationenergy as that exposed to the bypass diode 15.

[0059] This example is particularly effective when one bypass diode isconnected to each solar cell module and the relative comparison of thetemperature of the bypass diodes can not be executed.

EXAMPLE 5

[0060]FIG. 10 shows a construction material-integrated solar cell module(amorphous silicon solar cell BS-04 manufactured by CANON), according toExample 5 of the present invention. A solar cell module 10 is composedof five solar cells 10 connected in series, a bypass diode 15 isconnected to each of the solar cells 1. This example employed the solarcell module 10 in which one of the five solar cells 1 had a shortcircuit failure. A load was connected to the solar cell-module 10, andthe temperature of the bypass diode 15 connected to each of the solarcells was measured with a radiation thermometer. At the measurement, thesolar radiation energy was 0.7 kW/m², and the generated current was 3.5A. Table 3 shows the measured temperatures of the bypass diodes 15.TABLE 3 Solar cell No. 1 2 3 4 5 Bypass diode temp. (° C.) 47 46 46 4747

[0061] As seen from Table 3, the solar cell module 10 with the shortcircuit failure cannot be detected by measuring the temperature of thebypass diode 15.

[0062] Then the solar cells 1 within the solar cell module 10 werecovered one by one with a light shielding plate and the temperature ofeach bypass diode 15 covered was measured with a radiation thermometer.

[0063] Table 4 shows the measured temperatures of the bypass diodes 15.TABLE 4 Solar cell No. 1 2 3 4 5 Bypass diode temp. (° C.) 95 97 95 4895

[0064] As shown in this table, the comparison of the temperatures of thebypass diodes 15 indicates the absence of a current flowing in thebypass diode 15 of the fourth solar cell, thereby searching the shortcircuit failure in the fourth solar cell 1.

[0065] In this manner, it is possible to judge whether the solar cell 1has a short circuit failure, by covering the solar cells 1 one by onewith the light shielding plate and successively measuring thetemperatures of the bypass diodes 1.

[0066] In this example, the solar cells 1 were covered one by one withthe light shielding plate, but it is also possible to cover a pluralityof solar cells at the same time with the light shielding plate, as longas there can be secured a solar cell in a power generating state capableof supplying a current to the bypass diodes 15. Also when a plurality ofsolar cell modules 10 are connected in series, it is also possible toexecute the measurement by covering all the solar cells 1 within asingle solar cell module 10 at the same time.

[0067] Furthermore, the present example employed the solar cell module10 in which one bypass diode 15 is connected to each solar cell 1, butthe present example is likewise applicable to a case in which one bypassdiode is connected to a plurality of solar cells 1 or a case in which abypass diode is connected to a plurality of solar cell modules 10.

[0068] Also, in the present example, it is important to cover the solarcell 1 with the light shielding plate 80 and search the short circuitfailure in the solar cell 1 by judging whether a current flows in thecovered solar cell. Therefore, for detecting the presence of the currentflowing in the bypass diode 15, there may be employed the aforementionedcurrent detecting method by turning on the light emitting diode asdisclosed in Japanese Patent Laid-Open No. 8-97456 in addition to themethod of detecting the temperature rise in the bypass diode 15 asexplained in the present example, and there can also be applied variousother methods.

[0069] Also, if the connected bypass diode is in failure when the solarcell 1 is covered with the light shielding plate 80, an inverse voltageis applied to the solar cell 1 to induce a temperature rise therein. Itis therefore possible also to detect the failure in the bypass diode 15by covering the solar cell 1 with the light shielding plate 80 anddetecting the temperature of such solar cell 1.

[0070] According to the present invention, as explained in theforegoing, the temperature of the bypass diode in the solar cell moduleis detected from the exterior of the solar cell module, and the presenceor absence of a failure in the solar cell module is detected based onthe result of such temperature detection, so that the failed solar cellmodule can be searched from the surface of the solar cell. Also themanufacturing cost of the solar cell module can be reduced because thetemperature detection means need not be incorporated in advance in thesolar cell module. Also the failed solar cell module can be exactlysearched from the surface of the solar cell, because the failure isdetected by the mutual comparison of the results of temperaturedetection on the bypass diodes.

[0071] Furthermore, since the failed solar cell module is detected bydetecting a current flowing in the bypass diode connected to the coveredsolar cell, it is rendered possible to detect the short circuit failurewhich could not be detected in the prior art and also to detect afailure in the bypass diode.

[0072] Furthermore, the solar cell module of the present invention isprovided with the temperature detection means incorporated in the solarcell module and capable of detecting the temperature of the bypass diodeand the temperature of the interior of the solar cell module other thanthe bypass diode, so that the failure in the solar cell module can beexactly detected even in the case of employing the color changing memberincorporated in the solar cell module and capable of changing color inresponse to a temperature change.

[0073] Furthermore, as the bypass diode, an ordinary diode can be used,and therefore the forward voltage drop or the power loss can be reducedto minimize the loss in energy, in comparison with a case where thelight emitting diode is used.

[0074] Furthermore, since the failed solar cell module is detected bythe current generated by the solar cell, it is possible to detect thefailed solar cell module without interruption of the operation of thepower generating system which is required in the conventional case ofmeasuring the terminal voltage of the solar cell module.

[0075] Furthermore, as the means for detecting the temperature of thebypass diode and the temperature of the interior of the solar cellmodule other than the bypass diode, there can be employed a colorchanging member incorporated in the solar cell module and capable ofchanging color in response to a temperature change, whereby the failedmodule can be discovered visually and the work efficiency can beimproved.

[0076] Furthermore, by providing the vicinity of the bypass diode withthe means for preventing the temperature rise resulting from any causeother than a current, it is possible to prevent the temperature rise inthe bypass diode which is generated, for example, from the directsunlight and to securely discriminate the presence or absence of acurrent flowing in the bypass diode, thereby securely detecting thefailed solar cell module.

What is claimed is:
 1. A failure detecting method of detecting a failurein a solar cell module, which comprises detecting a temperature of abypass diode in a solar cell module from an exterior of the solar cellmodule, and detecting a presence or absence of a failure of the solarcell module based on a result of the temperature detection.
 2. A failuredetecting method according to claim 1, wherein the detection of thepresence or absence of the failure in the solar cell module is executedby mutual comparison of results of the temperature detection on eachbypass diode.
 3. A failure detecting method according to claim 1,wherein the temperature detection is executed by a temperature detectionmeans of non-contact type.
 4. A failure detecting method according toclaim 1, wherein the temperature detection is executed by a temperaturedetection means of contact type.
 5. A failure detecting method accordingto claim 1, wherein the solar cell module comprises, in a vicinity ofthe bypass diode, means for preventing temperature rise resulting from acause other than a current.
 6. A failure detecting method of detecting afailure of a solar cell module, which comprises covering at least onesolar cell in a solar cell module with a light shielding plate,detecting a current flowing in a bypass diode bypassing the coveredsolar cell, and detecting a failed solar cell module based on a resultof the current detection.
 7. A failure detecting method according toclaim 6, wherein the current detection is executed by detecting amagnetic force generated by the current.
 8. A failure detecting methodaccording to claim 6, wherein the current detection is executed by alight emitting member which emits light by the current.
 9. A failuredetecting method according to claim 6, wherein the current detection isexecuted by detecting a temperature of a bypass diode and/or a solarcell in the solar cell module.
 10. A failure detecting method accordingto claim 9, wherein the temperature detection is executed by atemperature detection means of non-contact type.
 11. A failure detectingmethod according to claim 9, wherein the temperature detection isexecuted by a temperature detection means of contact type.
 12. A failuredetecting method according to claim 9, wherein the temperature detectionis executed by a temperature detection means of visual type.
 13. Afailure detecting method according to claim 12, wherein the temperaturedetection is executed by a color changing member for showing a colorchange in response to a temperature change.
 14. A failure detectingmethod according to claim 13, wherein the color changing member is acolor changing member for showing a reversible color change in responseto a temperature change.
 15. A failure detecting method according toclaim 6, wherein the solar cell module comprises, in a vicinity of thebypass diode, means for preventing temperature rise resulting from acause other than the current.
 16. A failure detecting apparatus fordetecting a failure in a solar cell module, comprising a temperaturedetection means for detecting a temperature of a bypass diode in a solarcell module from an exterior of the solar cell module.
 17. A failuredetecting apparatus according to claim 16, further comprising means fordetecting a presence or absence of a failure in the solar cell module bymutual comparison of results of temperature detection on each bypassdiode.
 18. A failure detecting apparatus according to claim 16, whereinthe temperature detection means is of non-contact type.
 19. A failuredetecting apparatus according to claim 16, wherein the temperaturedetection means is of contact type.
 20. A failure detecting apparatusfor detecting a failure in a solar cell module, comprising a lightshielding plate for covering a solar cell module or a solar cell in thesolar cell module, a current detection means for detecting a currentflowing in a bypass diode bypassing the solar cell module or the solarcell, and means for detecting a failed solar cell module based on anoutput of the current detection means.
 21. A failure detecting apparatusaccording to claim 20, wherein the current detection means is means fordetecting a current by a magnetic force generated by the current.
 22. Afailure detecting apparatus according to claim 20, wherein the currentdetection means is means for detecting a current by a light emittingmember which emits light by the current.
 23. A failure detectingapparatus according to claim 20, wherein the current detection meanscomprises means for detecting a temperature of the bypass diode and/or asolar cell in the solar cell module.
 24. A failure detecting apparatusaccording to claim 23, wherein the temperature detection means is ofnon-contact type.
 25. A failure detecting apparatus according to claim23, wherein the temperature detection means is of contact type.
 26. Afailure detecting apparatus according to claim 23, wherein thetemperature detection means is a visual temperature detection means. 27.A failure detecting apparatus according to claim 26, wherein thetemperature detection means is a color changing member for showing acolor change in response to a temperature change.
 28. A failuredetecting apparatus according to claim 27, wherein the color changingmember is a member for showing a reversible color change in response toa temperature change.
 29. A solar cell module comprising a temperaturedetection means provided therein for detecting a temperature of a bypassdiode in the solar cell module and a temperature of an internal portionof the solar cell module other than the bypass diode.
 30. A solar cellmodule according to claim 29, wherein the temperature detection means ismeans for simultaneously detecting the temperature of the bypass diodein the solar cell module and the temperature of the internal portion ofthe solar cell module other than the bypass diode.
 31. A solar cellmodule according to claim 29, wherein the temperature detection means isa visual temperature detection means.
 32. A solar cell module accordingto claim 29, wherein the temperature detection means is a color changingmember for showing a color change in response to a temperature change.33. A solar cell module according to claim 31, wherein the colorchanging member is means for showing a reversible color change inresponse to a temperature change.
 34. A solar cell module with a bypassdiode, comprising, in a vicinity of the bypass diode, means forpreventing temperature rise of the bypass diode resulting from a causeother than a current.
 35. A solar cell module according to claim 34,wherein the means is a light shielding member or a heat insulatingmaterial.